System of voltage control



L. s. UPHOFF SYSTEM OF VOLTAGE CONTROL Filed'June 26, 1919 3 Sheets-Sheet 1 1": t ii 555% HHHHHHHHHHHmmm (Q. Q Q? Apr. 24, 1923. 1,452,857

L. S. UPHOFF v SYSTEM OF VOLTAGE CONTROL Filed 'June 26, 1919 I 3 Sheets-Sheet 2 id 2% i w a I :3; 2 3 I w (Um whoa Patented Apr. 24, 19 23.

umTEosT TEs LESLIE s. urnorr, 01* THE NITED STATES ARMY, ASSIGNOR TO THE SECRETARY or.

W. 1,452,857 PATENT OFFICE.

WAR OF- THE UNITED STATES OF AMERICA, TRUSTEE.

SYSTEM or VOLTAGE common Application filed June 26, 1919. Serial No. 306,99e.

, (FILED UNDER THE ACT or msacn 3, 1883, 22 Sum. 1., 625. X

To all wh'om it may concern:

Be it known that I, LESLIE S. UPHOFF, a citizen of the United States, stationed 'at l Washington, D. C. have invented an Improvement'in System'o'f Voltage .Control, of

which the fgllowing is a speclficatlon.

The invention described herein may be used by the Government,or any gf its ofiicers or employees in prosecution of work for the 0 Government, or by any other. person in'the -United States, without payment of any royalty thereon. p

.The subject of this invention is a system of voltage control adapted especially for use with X-ray machines.-

It has been customary is the cause-of many failures in taking pictures as the sparkterminals are often drawn essary because the penetrability of the rays depends on the voltage supplied and the number of rays controls the time of exposure.

change of current, viz., the number of milliamperes flowing through the tube, this change must be compensated for and the and eflicient methodfor compensating for such change. l

This system of' control is provided for by placing a voltmeter across .the main line;

volts per turn in the auto transformer constant and connecting a secondary voltage compensator-between-tlie auto transformer 'and the primary of the high tension transformer.

Of late years a self-rectifying tube has to determine the voltage in an X-ray machine by means of: measurement of the spark-gap. This is an inaccurate and unsatisfactory method and A change in v'oltage due toohmic resist-- anceof the circuit is experienced for everypresent system is devised to provide a ready connecting a line voltage adjuster, in the nature ofa switch, between the main linev and the auto transformer to maintain the,

come into use for X-ray machines, thus do- ;ing away with the rotary rectifier, so that a direct circuit leads from the transformer "to the tube. The present system of control for an X-ray machine I equipped wlthsuch a self-rectifying tube.

is adapted to care The present invention, therefore, aims to provide a system of voltage control for X- ray machines without the use of a spark gap or. kilovoltmeter.

With these objects in view, the invention .resides 1n thecombination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed can be made within the scope of what is claimed without departing from the spirit of the invention. 7

Practical embodiments of the invention are shown in the accompanying drawings,

Fig. 1 is a diagrammatic view of an X-ray equipment constructed in accordance with the invention;

a Fig. 2 is a similar view of thealternating equipment arranged in a slightly different manner; and

Fig. 3 is a chart of an alternating current -ray machine. Referring of a rotary rectifier 8, which in turnis con- 1 nected through the brushes 9-9 and circuit wires .10, tube 11;;

The milliammeter 12'is connected in series in the circuit 10 for the purpose of determin- 10' with the terminals of an X-ray to the drawings by numerals of reference ing the strength of the current furnished to the tube. One terminal 13 of the tube is a hot filament which is connected by circuit wires 14 to the secondary 15 of a transformer, the primary 16-of which is connected through line wires 17 and 17 with a suitable source of current supply. A veriable resistance 18, is provided in the li ne wire 17 and serves to regulate the current supplied to the filament so as to control the current passing through the tube.

. switch 31 which closes .the

a part of one branc For the purpose of the present invention, a voltmeter 19 is connected in parallel in the main line 1, and a switch 20, adapted to selectively engage contacts 21-,- which are joined by suitab e taps 22 to selected convolutions of the autotransformer 2, is interposed between one branch of the main line and the autotransformer for the purpose of maintaining the volts' per turn in the autotransformer constant.

A series of taps 23 are connected to selected convolutions of the autotransformer 2 and are provided with contacts 24, positioned to be selectively engaged, by a switch 25, which switch is ositioned in and forms or line of the circuit 3. These taps 23 are so'positioned on the autotransformer 2 as to cause a variatio'nin voltage equivalent to a selected variation in spark gap, say 1}". A switch 26 may also be provided in this branch of the circuit 3, for] the purpose of opening or closing the circuit as desired. At that end of the auto- 'transformer remote from the end at which tioned to be selectively engaged by a. switch 29, whichswitch is interposed in the other branch of the circuit This branch of the circuit, 3 is provided with a gap bridged by a fixed resistance 30 across which the current .may be shortscircuited by a g Referring to Figure 2, it.will be scent-hat the taps 27 are connected to the convolutions of the primary 4 of the transformer instead of being connected to the convolutions of the autotra-nsformer 2. In all other respects the arrangement of the system is the same and its" operation is that hereinbefore described in respect to Figure 1. The operation of the system as applied to alternating current device is as follows In making radiographs the operator uses such a combination of current and voltage inconnection with the X-ray tube as experience and practice has shown to bemost suitable for the size of the body to be radio-' graphed and the nature of the work. It is necessary, therefore, in doing general radiographic work to adjust the X-ray machine for various combinations of current and voltage from time to time. Suppose an operator decided, because of the nature of the gap (between fairly blunt points). In using a machine equipped with the system of voltclose switch 26 so as to apply the high volt-' age to the tube and adjust resistance 18 until the milliammeter 12 indicates 30 milliamperes. Since the machine is so calibrated that a voltage corresponding to a 5" gap is obtained when switch 25 is set on the point marked 5 and when the current indicated by milliammeter 12 corresponds to the setting of switch 29, the voltage actually obtained would be that which was desired, i. e. a 5" gap Voltage. Switch 29 isso arranged that the voltage drop caused by a given increment ofcurrent through the tube is exactly or approximately counterbalanced by an increase of voltage applied to' the primary of the high tension transformer from the line 4 The voltage sideof the autotransformer. across the tube must, therefore, always be as indicated by switch 25 provided the current through the tube is 'of the value indi cated" by switch 29. When switch 29 is arranged to counterbalance the voltage drop caused by given increments of current when switch 25 is at a given setting, it is also correct for every other setting of switch 25 for the following reasons:

Foran. auto-transformer having a small copper loss the present voltage drop is practically the same for any setting of switch 25. This isawell known characteristic of auto- -transformers. Therefore, if switch 29 is selectively varying the number of turns of the auto-transformer connected in the main line, a transformer connected to the autotransformer, means for selectively varying k the milliamperes of current supplied from the auto-transformer to the transformer, means graduated -in terms of spark gap for selectively varving the voltage supply from the auto-transformer to the transformer, and a rectifier connected to the transformer.

2. A system of voltage control, including a main line, a voltmeter in the main line. an auto-transformer, means for selectively va rying the number of turns of the auto-trans the auto-transformer to the transformer and former connected-inthe main line, a transmeans for adjusting the current supplied former connected to -the auto-transformer, from the transformer to agree with the milli- 10 means for selectively varying the milliamperes of current supplied from the auto- 5 amperes of current supplied from the autotransformer to the transformer.

transformer to the transformer, means for selectively varying the Voltage supply from LESLIE S. UPHO-FF. 

